1. Field of the Invention
The present invention relates generally to a vehicle front part structure, and more particularly to a front bumper beam and its vicinal structure.
2. Description of the Related Art
Known vehicles include front side frames provided rightwardly and leftwardly of front parts thereof. The front side frames extend longitudinally of the vehicles. Front bumper beams extending transversely of the vehicles are attached to front ends of the right and left front side frames. One example of the front parts of the vehicles thus arranged is disclosed in Japanese Utility Model Post-Exam Publication No. HEI-1-34940 entitled xe2x80x9cAUTOMOBILE FRONT PART STRUCTURExe2x80x9d.
The automobile disclosed in the publication includes upper front frames provided rightwardly and leftwardly of a front part thereof. The right and left upper front frames extend longitudinally of the automobile. Upper and lower branch frames extend forwardly from each upper front frame. The lower branch frame is formed integrally with the upper front frame. The upper branch frame is relatively short and coupled to the upper front frame typically by welding. Attached to front ends of the right and left upper branch frames is a front bumper extending transversely of the automobile. A front cross member extends between front ends of the right and left lower branch frames.
Upon a so-called xe2x80x9coffset collisionxe2x80x9d, that is, when a collision impact is applied to that part of the front bumper which is displaced from the center of the automobile toward either the right or left upper branch frame, the impact acts on the upper branch frame, disposed closely to that part, more strongly than on the other upper branch frame disposed remotely from that part.
If the coupling between the upper branch frame and the upper front frame is weakened by the impact, the upper branch frame with the thus-weakened coupling to the upper front frame loses efficiency in absorbing the impact. It is therefore desired of the upper branch frames to remain firmly coupled to the upper front frame even when subjected to the impact.
One may propose with respect to the right and left upper branch frames including right and left stays extending downwardly from front parts thereof that the front cross member extends between the lower ends of the stays. In this case, the right and left upper branch frames should be firmly or stably coupled to the stays so as to absorb the impact with increased efficiency. The upper branch frame coupled to the stays can be made steady by attaching additional members to the upper branch frame. However, the attachment of such additional members undesirably increases the weight of the automobile.
It is therefore an object of the present invention to provide a vehicle front part structure including right and left front side frames firmly or stably coupled to stays such that the weight of a vehicle does not increase and that, when the vehicle impacts on an object, the impact is absorbed with efficiency.
According to an aspect of the present invention, there is provided a vehicle front part structure comprising: right and left front side frames provided rightwardly and leftwardly of and extending longitudinally of a vehicle body; a front bumper beam attached to front ends of the right and left front side frames and extending transversely of the vehicle body; right and left stays extending downwardly from respective front parts of the right and left front side frames, the right and left stays each having first portions coupled through fastening members to and having second portions coupled through welding to the respective front parts of the right and left front side frames; and a front cross member through which lower parts of the right and left stays are connected to each other.
The stay has the first portions coupled through the fastening members to and has the second portions through the welding to the front part of the front side frame. The couplings between the front side frames and the stays are thus made strong. Even when the vehicle impacts on an object to thereby apply a larger force to one of the right and left front side frames than to the other front side frame, the right and left front side frames both remain firmly or stably coupled to the stays. The front parts of the right and left front side frames are firmly or stably coupled to each other through the right and left stays and the front cross member. The respective front side frames thus arranged buckle upon the impact of the vehicle on the object, thereby absorbing the impact with efficiency.
In a preferred form of the present invention, the right and left stays are coupled at the first portions to the front parts of the right and left front side frames more strongly than at the second portions.
Even when the second portions of the stay coupled through the welding to the front side frame are made unsteady by the impact of the vehicle on the object, the first portions of the stay coupled through the fastening members to the front side frame are kept steady. This means that the front side frame remains stably coupled to the stay.
In a further preferred form of the present invention, each of the right and left front side frames is halved to provide a rear frame and a front frame bolted to a front end of the rear frame, the front frame providing a smaller rigidity than the rear frame when the front bumper beam applies a load to the front frame.
When the vehicle impacts on an object, the impact acts on the front side frame. If the impact acting on the front side frame is small, the front frame alone deforms to thereby absorb the impact. The deformed front frame alone may be replaced. If the impact acting on the front side frame is large, the front and rear frames deform to thereby absorb the impact.
In a still further preferred form of the present invention, the front frame is polygonal in cross-section and is hollowed to define an interior space, the polygon having vertexes connected together through ribs provided within the interior space, the front frame and the ribs being integrally formed by extrusion.
The front frame is hollowed to define the interior space and has a polygonal cross-section. The polygon has the vertexes connected together through the ribs provided within the interior space. The front frame is formed by extrusion to thereby provide a constant thickness throughout the length thereof. The front frame thus arranged buckles uniformly along the length thereof, when the vehicle impacts on the object, to thereby absorb the impact with efficiency.